JPH10271829A - Rectifier circuit for general use inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rectifier circuit for a general use inverter which can suppress generation of harmonics as well as improve its power factor with a simple structure, reduce the size of a device, and conduct connection processing easily. SOLUTION: This rectifier circuit for a general use inverter a PWM converter as a basic structure. ON/OFF timing of an IGBT is controlled so that difference voltage may be zero based on a dummy input voltage signal generated from a dummy input voltage signal generating circuit 21, a signal based on the difference voltage between output voltage Vdc and a targeted value Vdc*, and input current detected by an AC current detector 17 in a control circuit 9' for controlling the ON/OFF of the IGBT which forms a bridge circuit 8 in the PWM converter. The dummy input voltage signal generating circuit 21 constituted of PLL detects the zero crossing point of the input current just after power input, conducts phase adjustment to the detected zero crossing point, and outputs a sinewave consisting of a predetermined peak value as the dummy input voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier circuit for a general-purpose inverter, and more particularly to a circuit for supplying a DC voltage within a certain range to an inverter circuit.

[0002]

BACKGROUND OF THE INVENTION General purpose inverters (VVVF) are used to supply power to pumps, motors, etc. in water treatment plants. As is well known, this general-purpose inverter includes a rectifier circuit 1 and an inverter circuit 2 connected in series.
(See FIG. 1).

That is, an input-side rectifier circuit 1 is connected to a commercial power supply, the commercial power supply (AC) is rectified, and then converted into an AC having a predetermined frequency by an inverter circuit 2 to load a load 3 such as a motor.
Power supply. And the rectifier circuit 1
For this purpose, a diode bridge circuit having a simple structure is generally used. In the case of such a diode bridge circuit, since the power factor is bad, a coil 4 is interposed in the preceding stage of the rectifier circuit 1 to improve the power factor.

In the conventional method of rectifying by using the rectifier circuit 1 composed of a diode bridge and the coil 4 described above, generation of harmonics cannot be prevented. Therefore, it is conceivable to use, for example, a circuit including a PWM converter as shown in FIG. 2 as the rectifier circuit. Such circuits are usually
It is used as a circuit for charging a battery in an uninterruptible power supply (UPS). That is, the AC voltage is rectified and converted into a DC voltage, and the DC voltage is applied to the battery to charge the battery.

[0005] The circuit will be briefly described.
Is connected to a bridge circuit 8 including an IGBT and a capacitor via an AC reactor 6, and the output of the bridge circuit 8 is connected to a load RL. A DC voltage is generated across the load RL. Conventionally, this load RL is the battery to be charged. The control circuit 9 controls on / off of the IGBT so that the output voltage Vdc becomes a constant DC voltage.

More specifically, the control circuit 9 compares the output voltage Vdc with the target voltage Vdc ^* in a first adder / subtractor 10, gives the difference to a first PI calculator 11, and generates a control signal corresponding to the difference. I do. That is, a command value is output such that the difference becomes zero. Therefore, when the output voltage Vdc is equal to the target voltage Vdc ^* , a command value that maintains the current state is output because the difference is 0. Then, the above command value is calculated by the multiplier 1
2 to one input terminal. On the other hand, an AC voltage detector 13 is connected to the output of the commercial power supply 5 and detects the voltage (input voltage) Vin of the commercial power supply 5. Then, the detected voltage Vin, that is, the input voltage (instantaneous value) is supplied to the other input terminal of the multiplier 12.

The multiplier 12 multiplies a given command value by a value corresponding to the input voltage to obtain a second adder / subtracter 16.
After subtracting the value detected by the AC current detector 17 therefrom, the signal is supplied to the third PI calculator 18 to generate a sine wave having a predetermined peak value. Then, the comparator 20 compares the sine wave generated by the second PI calculator 18 with the triangular wave output from the triangular wave generator 19, and controls the IGBT to be turned ON only in a section where the triangular wave is larger. . Note that the second adder / subtractor 16 subtracts a value based on the input current value when the deviation from the target value is large.
This is to prevent the peak value of the sine wave generated by the PI calculator 18 from largely changing.

The above operation principle will be described with reference to a waveform diagram as shown in FIG. First, the input voltage Vin becomes a sine wave composed of a certain frequency and a peak value as shown in FIG. It is also assumed that the relationship between the target value Vdc ^* and the output voltage Vdc is as shown in FIG. Then, the second PI calculator 18
Then, a sine wave synchronized with the input voltage is generated from the difference voltage and the input voltage as shown in FIG. The sine wave and the triangular wave output from the triangular wave generator 19 are compared by the comparator 20, and a pulse that is turned on only in the section where the triangular wave is higher is output from the comparator 20 as shown in FIG. You. Then, on / off of ITGB is controlled based on the pulse. At this time, the output voltage increases as the on-time increases.

Therefore, as the peak value of the input voltage increases, the peak value of the sine wave also increases, and control is performed such that the on-time is shortened. When the output voltage is smaller than the target value and the difference is large, the peak value of the sine wave is reduced so that the ON time is lengthened. As a result, even if the output voltage deviates from the target value, the output voltage converges to the target value, and even if the input voltage fluctuates, the output voltage follows immediately and becomes equal to the target value.

[0010] The PW mounted on the uninterruptible power supply described above.
The M converter is preferable in that it has a power factor of 1 and does not generate harmonics, but the circuit is complicated and two sensors, a current detector and a voltage detector, are required. In addition, if it is used as a rectifier of an inverter for driving the pump / motor or the like, the capacity of the AC reactor 6 is required to be twice as large as that of the uninterruptible power supply, so that the size of the AC reactor 6 is also extremely large, that is, twice or more. Become. As a result, if the AC reactor 6, the control circuit 9, and the bridge circuit 8 are to be housed in one case, the size of the case becomes large due to the AC reactor 6, and the loading and installation becomes complicated. In addition, even if the AC reactor 6 becomes large in size, the other circuit boards are not different from the conventional ones.
Occupies a large occupied area and space, which leads to an increase in the size of the entire device and a dead space around the device. Moreover, considering repair and replacement at the time of failure, the AC reactor 6
Are less likely to fail and are often other circuit parts.

Therefore, it has been considered to install the AC reactor outside the case. Then, only the bridge circuit and the control circuit are required for the case, and there is almost no dead space and the size can be reduced. In addition, there is an advantage that maintenance can be easily performed (for example, replacement is performed on a case-by-case basis). However, if such an AC reactor is installed outside, the AC current detector and AC voltmeter must also be installed outside, and wiring for connecting each detector to the circuit in the case is also required. This causes a new problem that the installation work becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object of the present invention is to solve the above-described problems and to suppress the generation of harmonics while improving the power factor with a simple configuration. Moreover, the size of the device can be reduced,
It is an object of the present invention to provide a rectifier circuit for a general-purpose inverter that can easily install a wiring process and the like.

[0013]

In order to achieve the above object, a rectifier circuit for a general-purpose inverter according to the present invention is a rectifier circuit installed on an input side of a general-purpose inverter.
A PWM converter has a basic configuration, and a switching element (IGB in the embodiment) of the PWM converter is used.
A control circuit for controlling ON / OFF of T) includes a pseudo input voltage signal generated from a pseudo input voltage signal generating means (PLL in the embodiment) and a signal based on a difference voltage between an output voltage and a target value. And controlling the on / off timing of the switching element based on the input current detected by the AC current detector so that the difference voltage becomes zero. Then, the pseudo input voltage signal generating means detects a zero cross point of the input current from the output of the AC current detector immediately after turning on the power, performs phase matching with the detected zero cross point, and has a predetermined peak value. A sine wave is output as a pseudo input voltage (claim 1).
The pseudo input voltage signal generating means can be realized by using, for example, a PLL-IC.

[0014]

FIG. 4 shows a preferred embodiment of a rectifier circuit for a general-purpose inverter according to the present invention. As shown in the figure, a commercial power supply 5 is connected to a bridge circuit 8 via an AC reactor 6 and the ON / OFF of an IGBT constituting the bridge circuit 8 is controlled by a control circuit 9 ′, so that an output is obtained. Voltage Vdc is the target voltage Vdc
It is the same as before in that it is set to ^* .

Here, according to the present invention, only an AC current detector 17 for detecting an input current is provided for sensing without providing an AC voltage detector, and a detection signal of the AC current detector 17 and an output voltage Vdc are controlled. The control signal is given to the circuit 9 '. That is, the control circuit 9 'includes P
A pseudo input voltage signal generation circuit 21 comprising an LL (Phase-Locked Loop) -IC is provided, and a pseudo input voltage (sine wave) signal V output from the pseudo input voltage signal generation circuit 21 is provided.
The IGBT is operated assuming that the peak value data of in 'and the zero-cross point (phase) are those of the input voltage from the commercial power supply 5, and control is performed so that the output voltage Vdc matches the target value Vdc ^* . As apparent from a comparison between FIG. 2 and FIG. 4, the configuration and the control algorithm are the same except that the pseudo input voltage is used instead of the actual input voltage. Description is omitted.

Next, the pseudo input voltage Vin 'output from the pseudo input voltage signal generation circuit 21 and the actual input voltage Vin
Will be described below. PLL-IC
Is, as is well known, a voltage controlled oscillator (VC
O), the frequency of the sine wave output and the frequency of the input carrier signal (output of the second PI calculator 18) are compared by a phase comparator (PC), and the output of the phase comparator (PC) is compared. Is fed back to the voltage controlled oscillator via a filter (LPF), and the input carrier signal and the PLL-
The IC operates so as to match the phase of the output signal Vin of the IC (output signal of the voltage controlled oscillator). In this embodiment, a comparator (C) having a reference voltage of 0 V is provided at each input of the phase comparator (PC), and a polarity signal (positive / positive) of each AC signal is provided.
Negative) is extracted, and the polarity signals are compared with each other. That is, the phases are adjusted so that the timings at which the polarities are inverted coincide.

The output voltage Vdc of the bridge circuit 8 is
In a normal operating state in which the input current substantially matches the target value, the input current has a pulsating flow, and cannot be used as information for detecting a zero-cross point of the input voltage. However, the input current when the IGBT is turned off immediately after the power is turned on has a waveform similar to a sine wave with almost the same phase as the input voltage. Therefore, the input current immediately after the power is turned on is detected by the AC current detector 17, the zero-cross point information of the detection signal is obtained, and the information is regarded as the zero-cross point of the input voltage to operate the PLL-IC. Therefore, the phase of the pseudo input voltage output from the PLL-IC immediately after the power is turned on is indirectly synchronized with the phase of the actual input voltage. Thereafter, it is assumed that the phase of the actual input voltage does not fluctuate, and PL
The control is performed by estimating the zero-cross point of the pseudo input voltage Vin 'output from the L-IC as the zero-cross point of the actual input voltage.
Therefore, even if the IGBT is turned on at an appropriate timing and the input current becomes a pulsating current, the zero cross point of the input voltage can be obtained. That is, the AC current detector 17 according to the present embodiment has a function of detecting a zero-cross point (phase) of the input voltage immediately after power-on, in addition to a function of suppressing a control signal for the IGBT from greatly fluctuating, as in the related art. Will have.

On the other hand, the peak value of the pseudo input voltage is set to be, for example, an ideal peak value of the commercial power supply 5 (of course, a specific peak value can be set arbitrarily instead of an ideal value). . That is, in this embodiment, since the input voltage is not actually sensed, it is not possible to detect a change in the input voltage from the input current. In this embodiment, the PLL
-Since the peak value of the voltage waveform output from the IC is fixed, it may be different from that of the actual input voltage. However, even if a deviation occurs, it is slight. In the present embodiment, control is performed by assuming that the peak value of the pseudo input voltage signal is set in advance (fixed).

In this way, if there is a deviation from the peak value of the actual input voltage, the response is deteriorated, but the output voltage Vdc is controlled so as to match the target value Vdc ^*. Therefore, even if there is a deviation in the peak value, the peak value will eventually match the target value. Since the load RL to which the output voltage Vdc is applied in the present embodiment is an inverter circuit, it is sufficient that a DC voltage is obtained within a certain range, so that even if the response is poor as described above, it functions without any problem.

As described above, in this embodiment, the PLL-IC
Since the pseudo input voltage signal output from is a signal that is substantially equal to the phase and peak value of the actual input voltage, even if the pseudo input voltage signal is regarded as the actual input voltage and the same control as in the related art is performed, The output voltage (DC) can be made to match the target value.

As a result, when actually manufacturing a general-purpose inverter device, as shown in FIG. 5, the AC reactor 6 and the AC current detector 17 are installed outside the case 22 and the bridge circuit 8 and the control circuit 9 ( REC) and inverter circuit 2
Can be stored in the case 22. In such a case, it is clear from comparison with FIG. 1 that the AC current detector 1 is a part that contacts the outside of the case even when compared with the conventional configuration.
7 (actually, the AC reactor 6 is used instead of the coil 4, but the number of components is the same in that part), and the connection processing also involves outputting the output signal of the AC current detector 17 to the control circuit 9 in the case 22. It is easy because it only needs to be connected. Since the large AC reactor 6 can be placed outside the case, the size of the case 22 can be reduced, and maintenance such as replacement of parts can be easily performed.

[0022]

As described above, in the rectifier circuit for a general-purpose inverter according to the present invention, the pseudo input voltage signal generating means (PLL) is used.
-IC), the pseudo input voltage signal output from the IC becomes a signal substantially equal to the phase and peak value of the actual input voltage.
Even if the pseudo input voltage signal is regarded as an actual input voltage and the same control as that of the related art is performed, the output voltage (DC) can be made equal to the target value. Therefore, the AC voltage detector, which is indispensable for the PWM converter mounted on the conventional uninterruptible power supply, is no longer necessary, and it can be used as a rectifier circuit for a general-purpose inverter that requires a large capacity and large AC reactor. Can be. And the power factor is improved to 1,
No harmonics are generated.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a configuration of a conventional general-purpose inverter.

FIG. 2 is a circuit diagram illustrating an example of a PWM converter used in the uninterruptible power supply.

FIG. 3 is a diagram for explaining the operation principle of the circuit of FIG. 2;

FIG. 4 is a circuit diagram showing a preferred embodiment of a rectifier circuit according to the present invention.

FIG. 5 is a schematic block diagram showing a configuration of a general-purpose inverter configured by using the present invention.

[Explanation of symbols]

 5 Commercial power supply 6 AC reactor 8 Bridge circuit 9 'Control circuit 17 AC current detector 21 Pseudo input voltage generation circuit RL Load (inverter)

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H02P 7/63 302 H02P 7/63 302R (72) Inventor Isao Takahashi 1603-1 Kamitomiokacho, Nagaoka City, Niigata Prefecture Inside Nagaoka University of Technology (72) Inventor Koji Utsunomiya 1 Kikyodaira, Ohira-mura, Kurokawa-gun, Miyagi Pref.

Claims (2)

[Claims] 1. A rectifier circuit provided on the input side of a general-purpose inverter, comprising a PWM converter as a basic configuration, wherein a control circuit for controlling on / off of a switching element in the PWM converter comprises a pseudo input voltage signal. A pseudo input voltage signal generated from the generating means, a signal based on a difference voltage between an output voltage and a target value, and the difference voltage based on an input current detected by an AC current detector installed on the input side. The on / off timing of the switching element is controlled so as to be 0, and the pseudo input voltage signal generation means detects a zero crossing point of the input current from the output of the AC current detector immediately after power-on. The phase is adjusted to the detected zero-cross point and a sine wave having a predetermined peak value is output as a pseudo input voltage. Rectifier circuit for general-purpose inverters. 2. The method according to claim 1, wherein the pseudo input voltage signal generating means includes
2. The system according to claim 1, wherein the system includes an L-IC.
The rectifier circuit for general-purpose inverters described in 1.